The present invention relates to a single-ended push-pull circuit (hereinafter referred to as SEPP circuit) and, more particularly, to an SEPP circuit suited as an inverter.
SEPP circuits have been widely used in logic and linear circuits. Particularly, such circuits are successfully applied in inverters used for level conversion or for driving an external load. In inverters used for these purposes, it must be taken into consideration that the power consumed at the time of change in output level should be small and that the inversion operation should not result in instability of other circuits driven by the same power source in addition to the basic requirement that the output satisfies the required output voltage level and changes rapidly.
There has been widely known a circuit formed of an input transistor receiving an input signal at its base, a first output transistor having a base connected to the collector of the input transistor, a second output transistor having a base connected to the emitter of the input transistor, and a circuit portion connecting the emitter of the first output transistor and the collector of the second output transistor to an output terminal. The collector-emitter paths of the first and second output transistors are connected in series. While the second output transistor receives a signal having a same phase as the input signal, the first output transistor receives the input signal after inversion by the input transistor. Thus, in theoretical operation, the first and second output transistors turn on and off, or off and on, respectively, at the same time. However, in practice, a transistor has a delay time for switching its operational condition. Due to this delay time, after the polarity of the input signal changes, there is a time duration when both of the output transistors keep their on-state causing flow of so-called "through-current" through the emitter-collector paths of both output transistors. This results in lowering of the voltage of the power source. This through-current results in not only an increment of power consumption but also in instability of the circuit operation of other circuits driven by the same power source.